You should approach your mix with attention to the three main dimensions in the sound field. They are height, width, and depth. Work on them each one at a time. Here's how...
Dimension 1:
Before starting the initial mixdown of all recorded tracks, set your mixer to MONO at first. (Don't worry, it's only temporary.) Don't bother with effects yet either, it's all about volume levels (height) at this point.
Now start a basic mix with everything in mono. You will notice it is far easier to determine proper levels for each track. Because everything will appear dead center, you can focus on its vertical size with no other dimensions to distract you. Pay close attention to anything that stands out too loud (too tall) or too quiet (too short.) Don't make everything the same level either. It all has its proper place in the mix as far as vertical size. The taller you make a certain instrument, the more the listeners will focus on it.
Dimension 2:
Listen to it several times that way until you feel that it has a good overall balanced sound. After you are happy with the volume levels in general, you can start adding effects to give depth to a few things, (your second dimension.) Reverb is effective at making things seem far away or smaller. This is done by changing the wet to dry ratio. The wetter the blend, the farther away a track may appear.
Dimension 3:
The third and last dimension should be Panning. With your mixer set back to stereo mode, you can now move instruments left or right. You should find that even after everything is panned out to its own private spot, (left or right in the sound field,) it all still mostly maintains that original blended volume.